1. The Field of the Invention
This invention relates generally to the field of electrical connector systems for electrical components. In particular, embodiments of the present invention relate to a shielding configuration that is particularly useful for use with user-removable, electronic modules that interface with a port of a host device. For example, embodiments of the present invention may find particular use with opto-electronic transceiver modules used to interface a host device with an optical communications network.
2. The Relevant Technology
Fiber optics are increasingly used for transmitting voice and data signals. While optical communications provide a number of advantages, the use of light as a transmission medium presents a number of implementation challenges. In particular, the data carried by a light signal must be converted to an electrical format when received by a device, such as a network switch. Conversely, when data is transmitted to the optical network, it must be converted from an electronic signal to a light signal. A number of protocols define the conversion of electrical signals to optical signals and transmission of those optical, including the ANSI Fibre Channel (FC) protocol. The FC protocol is typically implemented using a transceiver module at both ends of a fiber optic cable. Each transceiver module typically contains a laser transmitter circuit capable of converting electrical signals to optical signals, and an optical receiver capable of converting received optical signals back into electrical signals.
Typically, a transceiver module is electrically interfaced with a host device—such as a host computer, switching hub, network router, switch box, computer I/O and the like—via a compatible connection port. Moreover, in some applications it is desirable to miniaturize the physical size of the transceiver module to increase the port density, and therefore accommodate a higher number of network connections within a given physical space. In addition, in many applications, it is desirable for the module to be hot-pluggable, which permits the module to be inserted and removed from the host system without removing electrical power. For example, the Small Form-factor Pluggable (“SFP”) Transceiver MultiSource Agreement (“MSA”) was implemented to standardize the physical size and shape of optical transceiver modules to insure compatibility between different manufacturers. In SFP modules, usually a transceiver module is selectively removable from a port which is fixedly attached to the chassis or housing of the host device.
Another design consideration is the amount of electromagnetic interference (EMI) that is radiated by a certain component, module, or system. Equipment such as high speed data systems generate and transmit many signals in the radio frequency portion of the electromagnetic spectrum. EMI radiation is of concern because interference to other components or equipment may result if sufficient power from these signals escapes the equipment enclosures. Such interference may result in malfunctioning of some or all of the electronic system. EMI radiation may also limit the density of components in the system. Various national and international regulatory agencies (e.g., FCC, CISPR, etc.) have set limits for EMI emissions.
Nevertheless, many conventional transceiver configurations lack the ability to adequately reduce EMI emissions. Furthermore, conventional EMI shielding mechanisms often complicate the extraction of the module from the host port, even requiring at times the use of a special extraction tool to allow for access and retrieval of a module in order to not disturb adjacent modules and/or cables. Use of an extraction tool is often not desirable because it raises costs, can be misplaced, and may not be compatible with other module designs.
Therefore, there is a need for a module, such as an optical transceiver module, that has adequate EMI shielding when disposed in the host port and that still complies with existing standards. At the same time, the transceiver module should be easily inserted and extracted from a port without the need for a special extraction tool. Such a module having adequate EMI shielding would allow host systems to provide a higher packing density, and yet allow the use of small form factor transceiver modules that comply with existing sizing standards.